Tuesday, September 21, 2010

Video: How the Red Sea Could Have Parted

Biblical accounts of the Red Sea’s parting are hydrologically plausible, suggest computer simulations of sustained winds in a coastal lagoon where the Nile met the Mediterranean 3,000 years ago.

Under steady 60-mph winds, “the ocean model produces an area of exposed mud flats where the river mouth opens into the lake,” wrote National Center for Atmospheric Research oceanographers Carl Drews and Weiqing Han in an August 30 Public Library of Science One study. “These mud flats represent the area of crossing, and the crossing party would observe water to their left and right.”

In the Book of Exodus, Moses is described as leading Israelite slaves in flight from Egypt, arriving at the Red Sea’s shores just ahead of pursuing armies. At that point, “Moses stretched out his hand over the sea; and the Lord caused the sea to go back by a strong east wind all that night, and made the sea dry land, and the waters were divided.”

Han and Drews, who hosts a website dedicated to the compatibility of science and Christian faith, don’t consider the Exodus narrative to be literally true, but rather “an interesting and ancient story of uncertain origin.” Others have been similarly intrigued, suggesting that a rare phenomenon called wind setdown could have created dry passage across the Red Sea’s narrow northern tip. A wind setdown is essentially the flip side of a storm surge; when strong, steady winds cause water to rise dramatically in some areas, it necessarily drops in others.

In 1879, theologian Samuel Bartlett proposed a setdown location at a shallow inlet near of Suez, used by Arabs to cross the Red Sea at low tide. More recently, Russian researchers Naum Voltzinger and Alexei Androsov calculated that a 74-mph wind could have exposed an underwater reef near what is now the Suez Canal.

In the new study, Han and Drews determined that the depressions in the reef would have stayed underwater. They propose a different location, 75 miles north of the reef and just south of the Mediterranean, in what is now known as the Kedua Gap. The area is now dry, but historical reconstructions suggest an ancient branch of the Nile once flowed into a lagoon there.

After using satellite measurements and archaeological records to create a model of local hydrogeography, the researchers ran simulations that found 12 hours of 60-mph easterly winds would have exposed a dry passage, 2 miles long and 3 miles wide, out of Egypt.

When the winds stopped blowing, the waters would surge back, appearing in the researchers’ words “as an advancing wall of churning water” — or, per Exodus, “the waters returned, and covered the chariots, and the horsemen, and all the host of Pharaoh that came into the sea after them; there remained not so much as one of them.”

“If a crossing actually took place here, any debris field of military artifacts should be found to the north of the gap,” wrote Han and Drews.